/Engine/Plugins/Runtime/MeshModelingToolset/Source/ModelingComponents/Public/Drawing/PolyEditPreviewMesh.h
"Inset Type" duplicates the input faces and insets them using FInsetMeshRegion
void InitializeInsetType ( const [FDynamicMesh3](API\Runtime\GeometryCore\DynamicMesh\FDynamicMesh3) * SourceMesh, const [TArray](API\Runtime\Core\Containers\TArray)< int32 > & Triangles, const FTransform3d * MeshTransform )